Most cochlear implant (Cl) users, both adult and young, perceive speech remarkably well in quiet. Unfortunately, speech perception in noisy backgrounds, the ability to discriminate different talkers, the ability to discriminate different emotions in speech, music recognition, and tone-identification (for tone-languages such as Cantonese) are all still very difficult for Cl users. Poor perception of the pitch of complex tones (i.e., perception of fundamental frequency) is thought to be a primary contributing factor to these difficulties for Cl users. However, nearly all research on pitch perception by Cl users is based on adult Cl users, and may not apply to children who are implanted at a very early (VE) age. In a post-lingually deafened adult Cl user, electrical stimulation of the auditory nerve is subsequently processed by auditory neural pathways that had developed normally; pathways that, for example, once preserved a good tonotopic map at the auditory cortex due largely to the fine mechanical tuning of a normal, intact basilar membrane in the cochlea. VE Cl users, by contrast, would have electrical stimulation of the auditory nerve drive the development of subsequent auditory neural pathways, and hence these users may develop alternate mechanisms for processing auditory nerve signals. In particular, alternate mechanisms may be developed for perceiving complex pitch. Hence, the hypothesis to be tested in this proposal is: congenitally-deafened children, who receive a cochlear implant at a very early age (< 18 months old), can perceive the pitch of complex tones better than post-lingually deafened adult Cl users can. For both VE and adult Cl users, pitch perception will be assessed directly with synthesized, complex tones, and indirectly with speech stimuli using tasks that are thought to rely on fundamental frequency cues. Because FDA approval was given just 41/2 years ago for cochlear implantation at 12 months of age, it is only now possible to test this hypothesis with a substantial number of children in 1 local area, who fit the VE implantation criterion and who will soon be old enough (4-5 years) to engage in multiple experimental sessions. Results from this study may have a major impact on the clinical use and design of Cl processing strategies (different Cl processing strategies may be warranted for VE vs. adult Cl users), and on our understanding of auditory perceptual mechanisms that develop with atypical sensory inputs. This research will investigate the possibility that deaf children who receive a cochlear implant at a very early age will develop pitch perception abilities that exceed those of adults with cochlear implants (who were deafened after childhood). The results of this research could affect the design of cochlear implants and the speech perception benefits that cochlear implant users receive. [unreadable] [unreadable] [unreadable]